Issue 49

A. En-najiet alii, Frattura ed Integrità Strutturale, 49 (2019) 748-762; DOI: 10.3221/IGF-ESIS.49.67

C ONCLUSION AND OUTLOOK

T

he objective of this work was to characterize the thermal and mechanical behavior of a thermoplastic flat sheet. The elevated temperature tensile test was considered as the most practical and accurate approach for the actual deformation state during loading, and this technique was used to describe the damage to the various thermomechanical characteristics: resistance, elasticity modulus, and elongation. A comparison of the ABS mechanical characteristics enabled us to determine the performance of this material by exposing it to a tensile test coupled with temperature until the material was damaged. The evolution of the different parameters obtained allowed us to compare the temperature effects on the ABS mechanical behavior. Thereafter, we confirmed the ductile behavior of these, and we focused on comparing and processing the obtained curves. The increase in temperature demonstrated the critical impact on the material parameters and failure time. Indeed, the proposed approach consists of analyzing the evolution of the global geometry of the curves by considering the zones and characteristic points of these curves, and also takes into account the temperature effect, following the damage evolution by means of a static model. Two main zones were distinguished: the industrial zone, in which the configuration of the macromolecular chains was largely immobile and the temperature was below the glass temperature Tg = 110°C; and the thermoforming zone, in which the temperature was above the glass temperature Tg = 110°C. The macromolecular chains then tended to move more freely as the temperature increased, and thereafter the different stages of the process were determined. Using the results of this work, we can construct a solid maintenance strategy and make the work with polymers more efficient and simpler. Moreover, the simplified approaches proposed allow for clients and industrial companies to evaluate the damage based on static tests alone, without performing dynamic tests. Furthermore, these can provide a tool that can aid in conducting rapid and relevant checks for the quality control of this material. Finally, these results have demonstrated the feasibility of the applied damage approach. The proposed approach involves the material intrinsic parameters (elasticity modulus, elongation, and temperature), which enables a rigorous description of the material damage conditions. These preliminary studies are essential steps for complete realization of our medium-term objectives for the implementation and development of modeling and simulation tools for thermoplastic forming processes.

N OMENCLATURE

γe=σe/σa: Non-dimensional endurance limit γu= σu/σa: Parameter reflecting strength of material in virgin state γ=σur/σa: Parameter characterizing effect of damage on material mechanical characteristics σu: Endurance limit of the virgin material σur: Residual ultimate stress of material at different hole diameters σa: Applied stress level m: Material parameter D: Damage (D = 0 for neat material, D = 1 for completely damaged material) β: Life fraction for stress and Young's modulus in the industrial zone β': Life fraction for elongation in the industrial zone. θ: Life fraction for stress and Young's modulus in the Thermoforming zone θ': Life fraction for elongation in the Thermoforming zone Tg: Glass transition temperature

Tf: Melting temperature Ta: Ambient temperature Ti: Instant temperature

R EFERENCES

[1] Lligadas, G., Ronda, J. C., Galia, M. (2013). Renewable polymeric materials from vegetable oils: a perspective Caradiz Materials Today, 16(9). DOI: 10.1016/j.mattod.2013.08.016.

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